Hypersonic aerodynamics is a special branch of the study of
aeronautics.
The chief characteristic of hypersonic aerodynamics is that the
temperature
of the flow around the aircraft is so great that the chemistry of the
gas
must be considered. At low hypersonic speeds, the molecular bonds
vibrate, which changes the magnitude of the forces generated by
the air on the aircraft. At higher hypersonic speeds, the molecules
break apart producing an electrically charged
plasma
around the aircraft. Large variations in
air density
and
pressure
occur because of
shock waves, and
expansions.
Hypersonic aircraft typically have very thick
boundary layers
along the surface and high
heat transfer
to the surface.
All of these high speed flow phenomena lead to a vehicle design
unlike the typical airliner or fighter aircraft.

There are three principle aircraft
missions
to be considered in hypersonics; re-entry from orbit,
hypersonic cruise, and hi-speed accelerator, which can be used as
a re-usable booster. The first mission involves slowing a high speed
vehicle while the latter two missions require a highly
efficient propulsion system.
Because of the high stagnation temperatures present at hypersonic
speeds, a combination of
gas turbine propulsion for low speed
operations,
ramjets for high supersonic
propulsion , and
scramjets
for low hypersonic speeds has been proposed as a propulsion system.
The transitions between the various modes of propulsion is
an area of research.
The only piloted hypersonic vehicles (X-15, Space Shuttle, and a variety
of space capsules)
have all been
rocket powered.

This site was
prepared at NASA Glenn
to provide background information on hypersonic aerodynamics
for undergraduates, professionals, and life-long learners.
There is a particular emphasis here on the
math and science involved with high speed aerodynamics.
High school students should be able to make sense of the
math and science principles.
We include many, small, interactive
calculators and simulators
which solve the flow equations and are provided to aid your understanding.

This site has been intentionally organized to mirror
the unstructured nature of the world
wide web. There are many pages here connected
to one another through hyperlinks and you can then navigate through
the links based on your own interest and inquiry.
There is an index of topics that you
can access from any page, so you are never more than two clicks
away from any other Web page at this site.
However, if you
prefer a more structured approach, you can also take one of our
Guided Tours through the site. Each tour
provides a sequence of pages dealing with some aspect of aerodynamics.

NOTICE ---
The site has been developed to support Section
508 of the Rehabilitation Act. Many of the pages contain mathematical
equations which have been produced graphically and which are too
long or complex to provide in an "ALT" tag. For these pages, we
have retained the non-compliant graphic at the top of the page
and have provided a compliant text version of the equations in the
body of the page. In many cases, because of the use of Greek fonts in the
graphics, the purely English text version of the equations is slightly
different than the graphic version. The differences are noted in the text.